1. Field of the Invention
This invention relates to an image sensing apparatus and to a method of controlling this apparatus. More particularly, the invention relates to an image sensing apparatus equipped with both an optical zoom function and an electronic zoom function, and to a method of controlling this image sensing apparatus.
2. Description of the Related Art
The prior art includes an apparatus which, when a zoom switch is operated, transitions from optical zoom to electronic zoom to thereby display on a display device an enlarged image the magnification of which exceeds the maximum magnification provided by optical zoom. Also known is an apparatus that displays an electronically zoomed image between optical-zoom magnifications that change in stepwise fashion (see Patent Documents 1 and 2).
An electronically zoomed image has a resolution that, in general, is inferior to that of an optically zoomed image. There is also an apparatus in which an image-contour correction is performed in accordance with the zoom magnification in order to maintain resolution (the sharpness of contours, for example) in an electronically zoomed image (see Patent Documents 3, 4 and 5).
Patent Document 1: Japanese Patent Application Laid-Open No. 2006-32576
Patent Document 2: Japanese Patent Application Laid-Open No. 2005-62633
Patent Document 3: Japanese Patent Application Laid-Open No. 2005-20061
Patent Document 4: Japanese Patent Application Laid-Open No. 11-168653
Patent Document 5: Japanese Patent Application Laid-Open No. 3-218173
Patent Documents 3 to 5 change the strength of contour correction processing, which is executed with respect to image data, or the frequency hand for executing this contour correction processing, in accordance with the magnification of electronic zoom. However, contour correction processing suited to an electronically zoomed image is applied even to image data that has not been electronically zoomed and whose resolution is satisfactory, there is the danger that, contrary to expectation, degradation of the image-quality characteristic, such as the appearance of artifacts and blurring, will occur.